Devices for tensioning a safety belt comprising a pyrotechnic linear drive are known. It is also known that the linear drive of such a device may include a gas generator comprising an ignition unit and a protective cap to secure the gas generator before and during the construction of the gas generator.
In a vehicle collision, the belt slack of a safety belt which is being worn can be eliminated by a belt- or buckle tensioner. Various drive designs are known for such devices. Tensioning devices with pyrotechnic linear drives usually have a piston/cylinder unit, the piston representing a drive element accelerated by the compressed gas provided by the gas generator, the movement of which is used for the belt tensioning. If the belt tensioner is equipped with a force-limiting arrangement, the belt band force acting on the occupant can be reduced through a controlled decrease of the kinetic energy of the vehicle occupant. In order to ensure protection for the persons involved during transportation and during the assembly of the gas generator of the pyrotechnic linear drive, the gas generators are provided with a protective cap. The protective cap additionally offers protection from damage and also from moisture, dirt and the like. On assembly of the linear drive, the protective cap is then removed, in order to couple the gas generator to the piston/cylinder unit.